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Dear colleagues, Apologies to those of you receiving cross-postings. The following articles on Yangtze finless porpoise have recently been published: Vladimir V. Popov, Alexander Ya. Supin, Ding Wang, Kexiong Wang, Jianqiang Xiao, and Songhai Li. 2005. Evoked-potential audiogram of the Yangtze finless porpoise Neophocaena phocaenoides asiaeorientalis (L). J. Acoust. Soc. Am. 117 (5): 2728-2731. Songhai Li, Kexiong Wang, Ding Wang, and Tomonari Akamatsu. 2005. Echolocation signals of the free-ranging Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientialis). J. Acoust. Soc. Am. 117 (5): 3288-3296. Tomonari Akamatsu, Ding Wang, and Kexiong Wang. 2005. Off-axis sonar beam pattern of free-ranging finless porpoises measured by a stereo pulse event data logger. J. Acoust. Soc. Am. 117 (5): 3325-3330. Tomonari Akamatsu, Ding Wang, Kexiong Wang, and Yasuhiko Naito. 2005. Biosonar behaviour of free-ranging porpoises. Proc. R. Soc. B. 272(1565): 797-801. ABSTRACT Vladimir V. Popov, Alexander Ya. Supin, Ding Wang, Kexiong Wang, Jianqiang Xiao, and Songhai Li. 2005. Evoked-potential audiogram of the Yangtze finless porpoise Neophocaena phocaenoides asiaeorientalis (L). Evoked-potential audiograms were obtained in two (one male and one female) Yangtze finless porpoises, Neophocaena phocaenoides asiaseorientalis. Sinusoidal amplitude-modulated 20-ms tone bursts were used as probes with recording envelope-following evoked potentials. A frequency range of 8 to 152 kHz was investigated. The range of greatest sensitivity covered frequencies from 45 to 139 kHz, and the lowest thresholds of 47.2 and 48.5 dB re: 1 uPa were found at a frequency of 54 kHz in the two subjects, respectively. At lower frequencies, threshold increased with a rate of around 14 dB/octave, and threshold steeply increased at 152 kHz. Songhai Li, Kexiong Wang, Ding Wang, and Tomonari Akamatsu. 2005. Echolocation signals of the free-ranging Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientialis). This paper describes the high-frequency echolocation signals from free-ranging Yangtze finless porpoise in the Tian-e-zhou Baiji National Natural Reserve in Hubei Province, China. Signal analysis showed that the Yangtze finless porpoise clicks are typical high-frequency narrow-band (relative width of the frequency spectrum Q=6.6+/-1.56, N=548) ultrasonic pulses. The peak frequencies of the typical clicks range from 87 to 145 kHz with an average of 125+/-6.92 kHz. The durations range from 30 to 122 us with an average of 68+/-14.12 us. The characteristics of the signals are similar to those of other members of the Phocoenidae as well as the distantly related delphinids, Cephalorhynchus spp. Comparison of these signals to those of the baiji (Lipotes vexillifer), who occupies habitat similar to that of the Yangtze finless porpoise, showed that the peak frequencies of clicks produced by the Yangtze finless porpoise are remarkably higher than those produced by the baiji. Differenc! e in peak frequency between the two species is probably linked to the different size of preferred prey fish. Clear double-pulse and multi-pulse reverberation structures of clicks are noticed, and there is no indication of any low-frequency (<70 kHz) components during the recording period. Tomonari Akamatsu, Ding Wang, and Kexiong Wang. 2005. Off-axis sonar beam pattern of free-ranging finless porpoises measured by a stereo pulse event data logger. The off-axis sonar beam patterns of eight free-ranging finless porpoises were measured using attached data logger systems. The transmitted sound pressure level at each beam angle was calculated from the animal? body angle, the water surface echo level, and the swimming depth. The beam pattern of the off-axis signals between 45? and 115?(where 0?corresponds to the on-axis direction) was nearly constant. The sound pressure level of the off-axis signals reached 162 dB re 1 uPa peak-to-peak. The surface echo level received at the animal was over 140 dB, much higher than the auditory threshold level of small odontocetes. Finless porpoises are estimated to be able to receive the surface echoes of off-axis signals even at 50-m depth. Shallow water systems (less than 50-m depth) are the dominant habitat of both oceanic and freshwater populations of this species. Surface echoes may provide porpoises not only with diving depth information but also with information about surface di! rection and location of obstacles (including prey items) outside the on-axis sector of the sonar beam. Tomonari Akamatsu, Ding Wang, Kexiong Wang, and Yasuhiko Naito. 2005. Biosonar behaviour of free-ranging porpoises. Detecting objects in their paths is a fundamental perceptional function of moving organisms. Potential risks and rewards, such as prey, predators, conspecifics or non-biological obstacles, must be detected so that an animal can modify its behaviour accordingly. However, to date few studies have considered how animals in the wild focus their attention. Dolphins and porpoises are known to actively use sonar or echolocation. A newly developed miniature data logger attached to a porpoise allows for individual recording of acoustical search efforts and inspection distance based on echolocation. In this study, we analysed the biosonar behaviour of eight free-ranging finless porpoises (Neophocaena phocaenoides) and demonstrated that these animals inspect the area ahead of them before swimming silently into it. The porpoises inspected distances up to 77m, whereas their swimming distance without using sonar was less than 20m. The inspection distance was long enough to ensure a wide s! afety margin before facing real risks or rewards. Once a potential prey item was detected, porpoises adjusted their inspection distance from the remote target throughout their approach. The articles are available in PDF format by contacting [EMAIL PROTECTED] Please do not request reprints from the mail list. Best regards, XIAO, Jianqiang 17:31:29 2005-5-17 ================================================== XIAO, Jianqiang Institute of Hydrobiology The Chinese Academy of Sciences Wuhan, 430072 China [EMAIL PROTECTED], [EMAIL PROTECTED] ==================================================
